1953 film "Martin Luther"

I have a question I hope someone can help me with. I got the question second
hand so I'm not sure why the patron wants this information.
Apparently we have a patron who insisted to the reference department staff
that this film has to be in public domain because of it's age. (I know, age
often has very little to do with it, but oh well.) Anyway he wants to know
who has the rights to this film then since the reference people told him they
didn't think it was in the public domain.
I found that Louis de Rochemont Associates were the original distributors,
and Amazon has 2 versions for sale, one from Vision Video (which is where we
purchased our copy) and one from Vci Home Video.
If anyone can direct me to further information I would appreciate the help.
Thanks,
Karen Fischer
AV Librarian
Mansfield/Richland County Public Library
Mansfield, OH